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General Public Presentation
Diseases of Herbaceous Ornamentals
Brian D. Hudelson
Department of Plant Pathology
University of Wisconsin-Madison/Extension
• Causes – Pythium spp.
– Rhizoctonia solani
– Fusarium spp.
• Hosts: Any herbaceous ornamental
• Favorable environment: Cool, wet soils
Diseases of Herbaceous OrnamentalsDamping-Off/Seedling Blights
• Control– Use a pasteurized soil mixture
– Decontaminate pots/working surfaces/tools(10% bleach, 70% alcohol, disinfectants)
– Moderate soil moisture• Use a soil with adequate drainage
• DO NOT over-water
– Germinate seeds at higher temperatures
Diseases of Herbaceous OrnamentalsDamping-Off/Seedling Blights
• Control– Use fungicides to protect seedlings
• Captan
• Streptomyces lydicus
• Trichoderma spp., Gliocladium spp., Pseudomonas spp., Bacillus spp.
• Apply as a seed treatment or drench
Diseases of Herbaceous OrnamentalsDamping-Off/Seedling Blights
• Cause– Erysiphe spp. – Microsphaera spp.
– Uncinula spp. – Sphaerotheca spp.
– Phyllactinia spp. – Podosphaera spp.
– Blumeria spp. – Brasiliomyces spp.
– Oidium spp. – Ovulariopsis spp.
• Hosts: Virtually anything
• Favorable environment: High humidity
Diseases of Herbaceous OrnamentalsPowdery Mildews
2
• Control– Remove diseased plant material and debris
• Burn (where allowed)
• Deep bury
• Hot compost
– Reduce humidity• Plant less densely
• Thin existing stands
– Use resistant cultivars/varieties
Diseases of Herbaceous OrnamentalsPowdery Mildews
• Control– Use fungicides to prevent infections
• Dithiocarbamates, myclobutanil, propiconazole, tebuconazole, thiophanate-methyl
• Sulfur, neem oil, other plant-based oils
• Baking soda (1.5 Tbsp/gal) and light weight horticultural oil (3 Tbsp/gal)
• Alternate active ingredients (FRAC Codes)
• Apply when humidity >60-70%
• Apply at 7-14 day intervals
Diseases of Herbaceous OrnamentalsPowdery Mildews
• Cause: Plasmopara obducens
• Hosts – Standard garden impatiens (I. walleriana)
– Balsam impatiens (I. balsamina)
– Jewelweed (I. pallida, I. capensis)
– New Guinea impatiens (I. hawkeri)(resistant/tolerant)
• Favorable environment: Wet weather
Diseases of Herbaceous OrnamentalsImpatiens Downy Mildew
3
• Control– DO NOT grow impatiens in the same location
every year
– Grow tolerant/resistant/immune plants
– Start with clean transplants and seed
– Keep materials from different sources physically separated
– DO NOT overcrowd plants
– DO NOT overhead water
Diseases of Herbaceous OrnamentalsImpatiens Downy Mildew
• Control– Watch carefully for the disease
– Bag and discard affected plants• Symptomatic plants
• Asymptomatic surrounding plants
– Disinfest contaminated materials(70% alcohol, disinfectants, 10% bleach)
Diseases of Herbaceous OrnamentalsImpatiens Downy Mildew
• Control– Use fungicides to prevent infections
• Mancozeb
• Apply at 7 day intervals
Diseases of Herbaceous OrnamentalsImpatiens Downy Mildew
• Cause: Aureobasidium microstictum
• Host: Daylily
• Favorable environment: Wet weather
Diseases of Herbaceous OrnamentalsDaylily Leaf Streak
• Control– Promote rapid drying of leaves
• Divide large clumps
• Plant less densely
– DO NOT overhead water
– Remove diseased leaves and plant debris• Burn (where allowed)
• Deep bury
• Hot compost
Diseases of Herbaceous OrnamentalsDaylily Leaf Streak
4
• Control– Use varieties that are less susceptible
• ‘Betty Bennet’, ‘Edna Spalding’, ‘Ella Pettigrew’, ‘Globe Trotter’, ‘Nancy Hicks’, ‘Pink Superior’, ‘Ron Rousseau’, ‘Sudie’, ‘Tropical Tones’, ‘Upper Room’, ‘Winsome Lady’
– Use fungicides to prevent infections• Chlorothalonil, mancozeb, thiophanate-methyl
• Alternate active ingredients (FRAC Codes)
• Apply at 7-14 day intervals
Diseases of Herbaceous OrnamentalsDaylily Leaf Streak
• Pathogen: Puccinia malvacearum
• Hosts– Hollyhock
– Other plants in the mallow family
• Favorable environment– Wet weather
– Cool to moderate temperatures
Diseases of Herbaceous Ornamentals Hollyhock Rust
• Control– Buy rust-free hollyhock plants
– Grow rust resistant hollyhock varieties
– Remove weedy mallow species
– Promote rapid drying of leaves• Plant less densely
• Thin existing plant stands
Diseases of Herbaceous Ornamentals Hollyhock Rust
• Control– DO NOT overhead water
– DO NOT overwater
– Remove diseased leaves and plant debris• Burn (where allowed)
• Deep bury
• Hot compost
Diseases of Herbaceous OrnamentalsHollyhock Rust
• Control– Use fungicides to prevent infections
• Chlorothalonil, mancozeb, myclobutanil, tebuconazole, triticonazole
• Alternate active ingredients (FRAC Codes)
• Apply during periods of high moisture(particularly early in the growing season)
• Apply at 7-14 day intervals
Diseases of Herbaceous OrnamentalsHollyhock Rust
5
• Pathogen: Botrytis cinerea
• Hosts– Virtually any herbaceous plant
– Flowering plants• Geranium
• Peony
• Dahlia
• Favorable environment: Wet weather
Diseases of Herbaceous Ornamentals Botrytis Blight/Gray Mold
• Control– Remove infested plant debris/infect plant parts
• Burn (where allowed)
• Deep bury
• Hot compost
– Remove aging plant parts
– Promote rapid drying• Plant less densely
• Thin existing plant stands
Diseases of Herbaceous Ornamentals Botrytis Blight/Gray Mold
• Control– DO NOT overhead water
– DO NOT overwater
– Use fungicides to prevent infections• Chlorothalonil, copper, fludioxonil, mancozeb,
thiophanate-methyl
• Alternate active ingredients (FRAC Codes)
• Apply during periods of high moisture
• Apply at 7-14 day intervals
Diseases of Herbaceous OrnamentalsBotrytis Blight/Gray Mold
Diseases of Herbaceous OrnamentalsXanthomonas Leaf Diseases
• Causes: Xanthomonas spp.
• Hosts– Geranium – Begonia
– Poinsettia – Ivy
– Anthurium – Others
• Favorable environment: Wet weather
6
Diseases of Herbaceous OrnamentalsXanthomonas Leaf Diseases
• Control– Inspect plants before purchase
– Promote rapid drying of leaves• Plant less densely
• Thin dense stands
– DO NOT overhead water
– DO NOT handle plants when wet
– Be cautious carrying over plants from year to year
Diseases of Herbaceous OrnamentalsXanthomonas Leaf Diseases
• Control– Remove diseased leaves and plant debris
• Burn (where allowed)
• Deep bury
• Hot compost
– Disinfest contaminated materials(70% alcohol, disinfectants, 10% bleach)
– DO NOT use bactericides for control
Diseases of Herbaceous OrnamentalsRalstonia Wilt
• Cause: Ralstonia solanacearum– Races (host range-based classification)
– Biovars (sugar usage-based classification)
• Hosts– Geranium and other herbaceous ornamentals
– Vegetables (potato and tomato)
• Favorable environment: Warm, wet weather
Diseases of Herbaceous OrnamentalsRalstonia Wilt
• Control– Inspect plants before purchase
– Keep plants from different sources separated
– Disinfest contaminated materials(70% alcohol, disinfectants, 10% bleach)
– Routinely wash hands with soap and water
– If you suspect that you have this disease, contact the PDDC!
• Pathogen: Aster yellows phytoplasma
• Hosts– Many plants in the Asteraceae (aster family)
– Many other plants in many other plant families
• Favorable environment: None
• Vector: Aster leafhopper
Diseases of Herbaceous OrnamentalsAster Yellows
7
• Control– Remove diseased plants
• Hot compost
• Bury
• Burn (where allowed)
– Control leafhopper vector (?)
Diseases of Herbaceous OrnamentalsAster Yellows
• Cause: Tobacco mosaic virus (TMV)
• Hosts– Many herbaceous ornamentals
– Many vegetables
• Favorable environment: None
• Transmission: Mechanical– Touch
– Tools
Diseases of Herbaceous OrnamentalsTobacco Mosaic
• Control– Buy plants from a reputable source
– Inspect plants for symptoms
– Test plants prior to purchase
– DO NOT smoke around plants
– Wash hands routinely with soap and water
– Keep weeds under control
– Landfill diseased plants and plant debris
Diseases of Herbaceous OrnamentalsTobacco Mosaic
• Control– Disinfest contaminated materials
• 1% Sodium dodecyl sulfate (sodium lauryl sulfate) + 1% Alconox® (2½ Tbsp + 2¾ Tbsp/gal)
• Trisodium phosphate (14 dry oz/gal)
• 20% low fat dry milk (Carnation®) + 0.1% polysorbate 20 (9⅛ cups + ¾ tsp/gal)
• Alcohol dip followed by flaming
– DO NOT use chemical controls on plants
Diseases of Herbaceous OrnamentalsTobacco Mosaic
8
• Cause: Cucumber mosaic virus (CMV)
• Hosts– Many herbaceous ornamentals
– Many vegetables
• Favorable environment: None
• Transmission– Insect (aphids)
– Mechanical (contaminated tools)
Diseases of Herbaceous OrnamentalsCucumber Mosaic
• Control– Buy plants from a reputable source
• Inspect plants for symptoms
• Test plants prior to purchase
– Keep weeds under control
– Remove diseased plants and plant debris• Burn (where allowed)
• Deep bury
• Hot compost
Diseases of Herbaceous OrnamentalsCucumber Mosaic
• Control– Disinfest contaminated materials
• 1% Sodium dodecyl sulfate (sodium lauryl sulfate) + 1% Alconox® (2½ Tbsp + 2¾ Tbsp/gal)
• Trisodium phosphate (14 dry oz/gal)
• 20% low fat dry milk (Carnation®) + 0.1% polysorbate 20 (9⅛ cups + ¾ tsp/gal)
• Alcohol dip followed by flaming
– DO NOT use chemical controls on plants
– DO NOT use insecticides for aphid control
Diseases of Herbaceous OrnamentalsCucumber Mosaic
• Diseases– Tomato spotted wilt
– Impatiens necrotic spot
• Causes– Tomato spotted wilt virus (TSWV)
– Impatiens necrotic spot virus (INSV)
Diseases of Herbaceous OrnamentalsTospovirus Diseases
• Hosts– Many herbaceous ornamentals
– Many vegetables
• Favorable environment: None
• Transmission– Insects (thrips)
– Mechanical (contaminated tools)
Diseases of Herbaceous OrnamentalsTospovirus Diseases
9
• Control– Buy plants from a reputable source
• Inspect plants for symptoms
• Test plants prior to purchase
– Keep weeds under control
– Remove diseased plants and plant debris• Burn (where allowed)
• Deep bury
• Hot compost
Diseases of Herbaceous OrnamentalsTospovirus Diseases
• Control– Use insecticides to control thrips
– Disinfest contaminated materials• 1% Sodium dodecyl sulfate (sodium lauryl sulfate) +
1% Alconox® (2½ Tbsp + 2¾ Tbsp/gal)
• Trisodium phosphate (14 dry oz/gal)
• 20% low fat dry milk (Carnation®) + 0.1% polysorbate 20 (9⅛ cups + ¾ tsp/gal)
• Alcohol dip followed by flaming
– DO NOT use chemical controls on plants
Diseases of Herbaceous OrnamentalsTospovirus Diseases
• Cause: Hosta virus X (HVX)
• Host: Hosta– ‘Gold Edger’ ‒ ‘Striptease’
– ‘Gold Standard’ ‒ ‘Sum and Substance’
– ‘Golden Tiara’
• Favorable environment: None
Diseases of Herbaceous OrnamentalsHosta Virus X
• Transmission: Mechanical– Shovels
– Knives
– String edgers
– Lawnmowers
Diseases of Herbaceous OrnamentalsHosta Virus X
10
• Control– Buy hostas from a reputable source
• Inspect hostas for symptoms
• Test hostas prior to purchase
– Keep new and established hostas separated
– Remove diseased plants and plant debris• Burn (where allowed)
• Deep bury
• Hot compost
Diseases of Herbaceous OrnamentalsHosta Virus X
• Control– Disinfest contaminated materials
• 1% Sodium dodecyl sulfate (sodium lauryl sulfate) + 1% Alconox® (2½ Tbsp + 2¾ Tbsp/gal)
• Trisodium phosphate (14 dry oz/gal)
• 20% low fat dry milk (Carnation®) + 0.1% polysorbate 20 (9⅛ cups + ¾ tsp/gal)
• Alcohol dip followed by flaming
– DO NOT use chemical controls on plants
Diseases of Herbaceous OrnamentalsHosta Virus X
• Cause: Tobacco rattle virus (TRV)
• Hosts– Ornamentals
• Astilbe, bleeding heart, columbine, coral bells, daffodils, epimedium, gladiolus, hyacinth, marigold, peony, tulip, vinca
– Vegetables• Beans, beet, pepper, potato, spinach
• Favorable environment: None
Diseases of Herbaceous OrnamentalsTobacco Rattle
• Transmission – Stubby-root nematodes
• Trichodorus spp.
• Paratrichodorus spp.
– Mechanical
– Grafting
– Seed
Diseases of Herbaceous OrnamentalsTobacco Rattle
• Control– DO NOT buy symptomatic plants
– Grow non-susceptible plants• Annual phlox, carnation, devil’s trumpet (downy
thorn-apple), sweet William, zinnia, zombie cucumber
– Remove and destroy infected plants• Burn (where allowed)
• Deep bury
• Hot compost
Diseases of Herbaceous Ornamentals
Tobacco Rattle
11
• Control– Disinfest contaminated materials
• 1% Sodium dodecyl sulfate (sodium lauryl sulfate) + 1% Alconox® (2½ Tbsp + 2¾ Tbsp/gal)
• Trisodium phosphate (14 dry oz/gal)
• 20% low fat dry milk (Carnation®) + 0.1% polysorbate 20 (9⅛ cups + ¾ tsp/gal)
• Alcohol dip followed by flaming
Diseases of Herbaceous Ornamentals
Tobacco Rattle
• Control– DO NOT use chemical controls on plants
– DO NOT attempt to control stubby-root nematodes
Diseases of Herbaceous Ornamentals
Tobacco Rattle
• Cause: Aphelenchoides spp.
• Hosts– Many types of herbaceous plants
– Landscape plants• Hosta, begonia, coral bells, miterwort
– Houseplants• African violets, ferns, chrysanthemum
• Favorable environment: Wet weather
Diseases of Herbaceous OrnamentalsFoliar Nematode
• Control– Inspect plants prior to purchase
– Avoid overhead watering
– Remove symptomatic plants and plant debris• Burn (where allowed)
• Deep bury (landfill)
• Hot compost
Diseases of Herbaceous OrnamentalsFoliar Nematode
• Control– Disinfest contaminated materials
(70% alcohol, disinfectants, 10% bleach)
– Hot water treatments (10 minutes at 125°F)
– DO NOT use nematicides
Diseases of Herbaceous OrnamentalsFoliar Nematode
12
• Pathogen: Sclerotium rolfsii
• Hosts– Many herbaceous annuals and perennials
• Hosta
• Bedding plants
– Some woody ornamentals
• Favorable environment: Warm, wet weather
Diseases of Herbaceous OrnamentalsSouthern Blight
• Control– DO NOT buy infected/infested plants– Avoid cocoa mulch (?)– Remove infected plants, mulch and soil
• Double bag and landfill
– Disinfest contaminated materials(70% alcohol, disinfectants, 10% bleach)
Diseases of Herbaceous OrnamentalsSouthern Blight
• Control– Amend soil with organic matter (?)– Use fungicides for control
• Contract with a professional pesticide applicator• Azoxystrobin, flutolanil, flutolanil + thiophanate-
methyl, PCNB, tebuconazole, triadimefon• Alternate active ingredients (FRAC codes)• Apply at 14 – 28 day intervals
– Pray for a really, really, REALLY cold winter
Diseases of Herbaceous OrnamentalsSouthern Blight
• Pathogens – Pythium spp. – Phytophthora spp.
– Rhizoctonia solani – Fusarium spp.
– Cylindrocarpon spp. – Thielaviopsis spp.
• Hosts: Any herbaceous plant
• Favorable environment: Cool, wet soils
Diseases of Herbaceous OrnamentalsRoot/Crown Rots
13
• Control– Moderate soil moisture
• Grow plants in well-drained sites
• Use a potting mix with adequate drainage
• Improve drainage in poorly drained soils– Add organic matter to improve drainage
– Use raised beds
• DO NOT overwater
• DO NOT overmulch
Diseases of Herbaceous OrnamentalsRoot/Crown Rots
• Control– Pretest soils/mulches/composts
– Use a soil-less potting mix or a pasteurized potting mix for containerized plants
– DO NOT move contaminated soil or plants
– Disinfest contaminated materials(70% alcohol, disinfectants, 10% bleach)
Diseases of Herbaceous OrnamentalsRoot/Crown Rots
• Control– Use fungicides to prevent infections
• Contract with a professional pesticide applicator
• Etridiazole, metalaxyl, mefenoxam, fosetyl-Al, PCNB, thiophanate-methyl, fludioxonil
• Alternate active ingredients (FRAC codes)
• Use granular formulations if possible
• Use during periods of wet weather
Diseases of Herbaceous OrnamentalsRoot/Crown Rots
• Control– Use biopesticides to prevent infections
• Trichoderma, Gliocladium
• Use for potted plants
• Exercise caution when combining with chemical fungicides
Diseases of Herbaceous OrnamentalsRoot/Crown Rots
Diseases of Herbaceous OrnamentalsWhere to Go for Help
Plant Disease Diagnostics ClinicDepartment of Plant Pathology
University of Wisconsin-Madison1630 Linden Drive
Madison, WI 53706-1598(608) 262-2863
[email protected]://pddc.wisc.edu
Follow on Facebook and Twitter @UWPDDC